It is known in the literature that polymers containing aromatic rings may be crosslinked in a Friedel-Crafts type of reaction employing a halocarbon and a catalyst, such as aluminum chloride. Thus the aromatic ring containing polymer, for example polystyrene, may be crosslinked by reaction with poly(trichlorobutadiene) and aluminum chloride, V. Korshak, et. al., Vysokomol. Soedin., Ser. A, vol. 29, pp. 140-146 (1987), or with bis(chloromethyl)diphenyl, V. A. Davankov, et. al., Angew. Makromol. Chem., vol. 32, pp. 145-151 (1973).
U.S. Pat. No. 3,423,335 discloses the use of paraxylylene dihalides [1,4-bis(halomethyl)benzenes] to crosslink polymers containing aromatic rings that contain hydrogen atoms attached to these rings. These reactions are carried out at 150.degree. C. to 500.degree. C., with or without catalysts present. The instant invention does not involve the use of this type of halocarbon.
C. D. Nenitzescu, et. al., Ann., vol. 491, pp. 189-220, (1931) report the uncatalyzed reaction of benzyl chloride with compounds such as biphenyl, naphthalene, anisole and mesitylene to yield the corresponding diarylmethane. No mention is made of the use of polymers.
U. S. Pat. Nos. 2,631,993 and 2,734,045 provide for the crosslinking of certain polymers, all of which have nitrogen containing substituents, by reaction with halocarbons containing at least two halogen atoms. These processes are carried out at lower temperatures than the instant process, and, as stated in '993, are believed to occur because of quaternization of the nitrogen substituents. The present invention does not require nitrogen substituents.
It is the purpose of this invention to provide methods for crosslinking polymers containing aromatic ethers with halocarbons, wherein the crosslinking reaction is carried out without any catalyst present. This is advantageous in many cases since a catalyst may also catalyze other, unwanted, reactions, and the catalyst residues may have deleterious effects on the stability or other properties of the crosslinked polymer. Removal of catalyst residues can be costly and difficult.